The invention concerns a silencer (S1) intended to be fitted to an exhaust line (L) of a heat engine (M), and that comprises one or a plurality of envelope(s) that delimit three volumes (1 a,1 b, 2), referred to as upstream (1 a), intermediate (1 b) and downstream (2), traversed by a plurality of conduits, including: - a supply conduit (10) conveying the exhaust gases from the engine (M) to the intermediate volume (1b), passing through the upstream volume (1 a), - a so-called "outward" journey conduit (12) taking the exhaust gases from the intermediate volume (1 b) to the downstream volume (2), - a so-called "return" journey conduit (13) taking the exhaust gases from the downstream volume (2) towards the upstream volume (1 a), passing through the intermediate volume (1 b), and - a discharge conduit (14) taking the exhaust gases out of the silencer, either by means of a so-called "outward" journey from the upstream volume (1 a) to the downstream volume (2) from which it opens to the outside, or by means of a so-called "outward-return" journey from the upstream volume (1 a) to the downstream volume (2) and then once more to the upstream volume (1 a) from which it opens to the outside.